Difference in 3.7l Liberty and 3.7l WK engine?? - Jeep Garage - Jeep Forum

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Old 02-02-2015, 12:07 PM
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Difference in 3.7l Liberty and 3.7l WK engine??

I'm trying to figure this out. Why can I find an S load of performance mods for and '05 3.7l Liberty, but nothing for the WK 3.7l . Has anyone tried using a tuner from a Liberty on a WK? Please let me know what you find out! I'm very interested in seeing if anyone has tested these waters yet.

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Old 02-02-2015, 06:16 PM
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Re: Difference in 3.7l Liberty and 3.7l WK engine??

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Originally Posted by jisfalt88 View Post
I'm trying to figure this out. Why can I find an S load of performance mods for and '05 3.7l Liberty, but nothing for the WK 3.7l . Has anyone tried using a tuner from a Liberty on a WK? Please let me know what you find out! I'm very interested in seeing if anyone has tested these waters yet.
well this is a straight forward question, I will do my best to answer each part of it.

" Why can I find a ton of performance mods for the liberty 3.7, but not the wk 3.7?"

This is due to the 3.7 is the only engine available in a US spec liberty, whereas the WK has multiple V8's as an option, this basically left the aftermarket on the WK 3.7 almost non existent. But don't worry, there are parts out there for it.

"has anyone tried a tuner for a liberty on a wk?"

This isn't as simple as it sounds. Even tho the liby and the Wk have the same 3.7, there are some differences in drivetrain and calibrations. For example the liberty has a 4spd trans with a TCM intergrated in the PCM. The WK 3.7 (and SRT) have a different trans, the 5spd with a TCM inside the dash. Having the TCM in the dash in the WK makes it impossible to change TCM tunes for the trans without replacing the TCM itself.

Now there are a few tuners out for the WK 3.7. SCT has one for the 05 so you have something there.

As far as using the liberty mods in a wk, ill use my jeep as a prime example. they don't make headers for the wk 3.7, but they do for the liberty. I took liberty headers and bolted them to mine in the wk. for this to work you must order for an 05 and up liberty.

I hope this helps, please stop by my build thread if you need ideas or have any questions
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Old 02-10-2015, 03:25 PM
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Re: Difference in 3.7l Liberty and 3.7l WK engine??

Thank you, I really appreciate the advice. I have been reading your thread and watching your videos. I'm just now beginning to be able to put some money into her simply because I now own her.
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Old 02-16-2015, 04:14 PM
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Re: Difference in 3.7l Liberty and 3.7l WK engine??

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Originally Posted by jisfalt88 View Post
I'm trying to figure this out. Why can I find an S load of performance mods for and '05 3.7l Liberty, but nothing for the WK 3.7l . Has anyone tried using a tuner from a Liberty on a WK? Please let me know what you find out! I'm very interested in seeing if anyone has tested these waters yet.
I believe the Liberty has a different compression ratio, different intake plenum and different heads as well. There were some problems associated with the earlier 3.7's that were supposedly fixed with the 05 generation of motors.

The 3.7 is not a bad motor, but I don't see it becoming a superstar either..
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Old 02-16-2015, 04:21 PM
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Re: Difference in 3.7l Liberty and 3.7l WK engine??

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Originally Posted by GratefulDeadWK View Post
I believe the Liberty has a different compression ratio, different intake plenum and different heads as well. There were some problems associated with the earlier 3.7's that were supposedly fixed with the 05 generation of motors.

The 3.7 is not a bad motor, but I don't see it becoming a superstar either..
nope, all 3.7's have a 9.7 to 1 compression. the issues that were fixed mainly had to do with idle quality and noise reduction. a new cam profile and timing solved the idle quality issue while a thicker intake manifold and composite valve covers helped reduce noise. also in 2005 they went from the JTEC pcm to the NGC pcm
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Old 02-16-2015, 05:01 PM
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Re: Difference in 3.7l Liberty and 3.7l WK engine??

Is it true that using the Liberty headers, heat Wrapping them can cause the headers to crack? a buddy of mine said this, and while I was thinking about it, I'd like for them to stick around a while especially if I'm spending money.

I think to get the most out of what I can afford right now, I'm going to replace the Headers, o2 sensors (they've never been changed), and add a magna flow exhaust.
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Old 02-16-2015, 06:07 PM
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Originally Posted by jisfalt88 View Post
Is it true that using the Liberty headers, heat Wrapping them can cause the headers to crack? a buddy of mine said this, and while I was thinking about it, I'd like for them to stick around a while especially if I'm spending money.

I think to get the most out of what I can afford right now, I'm going to replace the Headers, o2 sensors (they've never been changed), and add a magna flow exhaust.
Yes. A member here tried it and destroyed his headers. Jba even states not to use wraps for the headers
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Old 02-19-2015, 02:35 AM
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Re: Difference in 3.7l Liberty and 3.7l WK engine??

Hi I am reading this posting with great interest.
Strongjeff, your input and comments are very valuable, thanks very much for sharing your knowledge.

What is the difference between the Libby and WK headers? What effect will the change do to the WK motor?
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Old 02-19-2015, 09:14 AM
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Originally Posted by skala View Post
Hi I am reading this posting with great interest.
Strongjeff, your input and comments are very valuable, thanks very much for sharing your knowledge.

What is the difference between the Libby and WK headers? What effect will the change do to the WK motor?
Hi there skala, unfortunately there is no headers made directly for the wk 3.7, but seeing how it's the same engine as the libby they will bolt right up.

However, in the wk there is some clearance issues to address durring the install.
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Old 02-19-2015, 09:59 AM
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And to pick up where I stopped...

On the passengers side you'll need to move the heater core lines up a few inches. I zip tied mine to the strut brace. On the drivers side there is a high probability of the a bracket that supports the steering shaft to run the header. You could put a small dent in the header to clear it or shave the bracket.

The bolts jba supplies to connect the mods to the headers are a low grade bolt. They are grade 5. You will need grade 8 for the higher temperature tolarance. These need to be checked often for tightness.

Improvements, there is a deffinate improvement in acceleration. I've seen a solid .3 tenths faster in the 8th mile. The engine loves it, loves to breathe and be wound out. Power comes in around 3k and pulls to red line.
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